This invention relates to the field of intravascular medical devices. More specifically, the present invention relates to a convertible catheter incorporating a force transfer mechanism for increasing the force transfer from a distally extending core wire to a proximal portion of the catheter.
Intravascular catheterization devices have proven to be useful and efficient for both therapeutic and diagnostic purposes. Intravascular therapeutic techniques, such as angioplasty, atherectomy, and laser irradiation, have been developed as alternatives to bypass surgery for treating vascular diseases or other conditions that occlude or reduce the lumen size of portions of a patient""s vascular system. In particular, balloon angioplasty has proven to be a useful and in many circumstances a preferred treatment for obstructive coronary diseases. Also, intravascular diagnostic techniques, such as ultrasonic imaging and Doppler blood flow measurements, have been developed to measure or image the extent of an occlusion of a vessel (e.g., stenosis). The devices used to perform the aforementioned intravascular therapeutic and diagnostic techniques may be used together or in conjunction with more invasive techniques such as coronary surgery.
These intravascular therapeutic and diagnostic devices have achieved acceptance because of their effectiveness as well as the fact that they can be used in a minor surgical procedure that is relatively nondisruptive to the patient compared to coronary surgery. These devices rely on the positioning of a catheter into the vascular system of a patient via an incision at an accessible location which may be remote from the site of the occlusion or stenosis. For example, the accessible location may be the femoral artery at the groin. The intravascular device is then advanced through the incision via the femoral artery to a desired coronary distal site. The distal sites into which the device may be advanced include the coronary arteries, branch vessels stemming from the external carotid artery such as the occipital and the arteries leading to the vessels of the head and brain, splenic, and the inferior mesenteric and renal arteries leading to the organs of the thorax as well as other vessels.
Because of the small size of some of these vessels and the tortuous passages through the vessels, positioning of a catheter device through a patient""s vasculature can be a difficult and time consuming task requiring considerable skill on the part of the physician. For example, in order to perform an angioplasty dilation, the angioplasty balloon catheter must be positioned across the stenosis in the arterial site. The stenosis may be located in a tortuous portion of the coronary vasculature and, furthermore, the obstructive arterial disease may impede crossing the stenosis with the balloon portion of the angioplasty catheter. Thus, not all arterial obstructions can be successfully treated by present intravascular balloon catheter procedures because some arterial obstructions are not readily accessible to a balloon dilation catheter. Accordingly, there is often a need for intravascular catheters of very low profile that can be positioned in narrow, tortuous regions of a person""s vasculature.
Another important consideration relating to intravascular procedures, such as angioplasty, relates to the exchange of various devices used to perform the procedures. Intravascular therapeutic and diagnostic devices come in various types and sizes suitable for the vessel size and location in which the treatment is to be performed. Sometimes, it becomes necessary to exchange a first therapeutic device for one of a different size after an unsuccessful attempt has been made to position the first device in the appropriate location. It may also become necessary to exchange therapeutic devices after the first device is successfully positioned in the desired location. This may be necessitated because it becomes apparent that the first device is the wrong size or configuration, or because it is determined that additional therapeutic or diagnostic procedures with a different size or type of device is required.
Several different types of catheter constructions have been developed for positioning intravascular therapeutic or diagnostic catheters through a patient""s vasculature. Two primary types of catheter constructions are the over-the-wire (OTW) type catheters and the single operator exchange (SOE) type catheters.
An over-the-wire type catheter includes a central lumen through the entire length of the intravascular device that can accommodate a separate guide wire that is movable, and removable, in relation to the catheter to facilitate positioning of the catheter in a remote vessel location over the guide wire. In the over-the-wire construction, the catheter typically includes a lumen adapted to receive the guide wire from a proximal end to the distal end of the device. The guide wire is initially loaded through the lumen of the over-the-wire catheter and extends out from the distal end thereof. Then, the guide wire and the intravascular catheter are advanced together and positioned in the vessel at the desired site. The guide wire may be advanced distally of the distal end of the catheter and steered, as necessary, to traverse tortuous passages of the vessel with the catheter subsequently advanced distally over the wire tracking the wires path. With the guide wire extending through the full length lumen, the guide wire provides some column support to the catheter shaft especially in the distal portion thereof. This improves the pushability of the catheter. The guide wire may then be withdrawn proximally through the lumen of the catheter or may be left in place extending from the distal end of the catheter during the procedure.
The over-the-wire type intravascular catheter facilitates exchanges because a first catheter can be exchanged with a second catheter without removing the guide wire. This allows an exchange of catheters without having to repeat the difficult and time consuming task of positioning the guide wire. In order to leave the distal end of the guide wire in place, it is preferred to maintain a hold on a proximal end portion of the guide wire during the exchange operation. One way to maintain such a hold is to use a guide wire having a sufficiently long length (e.g., 300 cm) so that the entire catheter can be completely withdrawn over the guide wire while maintaining a hold on a portion of the wire. A disadvantage of this method is that the long proximally extending portion of the guide wire may be in the way during the procedure. Another way to maintain a hold on a portion of the guide wire during an exchange operation is to use a guide wire extension. A disadvantage of this method is that not all guide wires are adapted to connect to an extension wire, and moreover, the step of connecting the guide wire to the extension wire can sometimes be tedious and difficult to perform.
A second type of catheter which facilitates the exchange of a first catheter with a second catheter is the single-operator exchange type construction. With the single-operator exchange type construction, a guide wire occupies a position adjacent and exterior to the intravascular catheter along proximal and intermediate portions of the catheter and enters into a short guide wire lumen of the catheter via an opening at a location close to a distal portion of the catheter. With this type of construction, the catheter can be positioned in the patient""s vessel by positioning a guide wire in the desired location and advancing the catheter device over the wire. An advantage of the short guide wire lumen is that in the event it becomes necessary to exchange the catheter, the position of the guide wire can be maintained during withdrawal of the catheter without the use of a long guide wire (e.g., 300 cm) or an extension wire. Because the proximal end of the guide wire is exterior to the proximal end of the catheter, the proximal end of the guide wire can be held during withdrawal of the catheter so that the position of the distal end of the guide wire in the patient""s vessel can be maintained. With this type of catheter, it is necessary that the distance from the distal end of the catheter to the proximal guide wire lumen entrance be less than the length of the guide wire that extends proximally out of the patient.
Although single operator exchange catheters make it easier to exchange catheters, the construction has two disadvantages. First, the guide wire running external to the catheter shaft does not provide any column support for the shaft nor does the shaft provide support for the wire if the wire is pushed distally to cross a lesion. Second, with the single operator exchange design, the guide wire can not be replaced while the catheter remains in the body.
Just as it is sometimes necessary to exchange an intravascular catheter, it may also become necessary to exchange the guide wire or otherwise assist in advancing the guide wire to the desired location in the vessel. After the guide wire and catheter are in the vessel, it may be determined that the size or shape of the guide wire is inappropriate for advancement to the desired position in a vessel. For example, the diameter of the guide wire may be too large for advancement past an extensive stenosis or occlusion in a vessel or for advancement in another relatively small vessel. The diameter of the guide wire may also be too small for effective advancement of the guide wire and catheter to the desired location in the vessel.
It may also be determined that the shape or construction of the guide wire is inappropriate for advancement of the guide wire to the desired position after the guide wire and catheter are in the vessel. For example, a distal portion of the guide wire is often bent a desired amount prior to insertion into the body of a patient to allow manipulation of the guide wire through various vessels. After the guide wire is in a vessel, it may be determined that a guide wire with a different xe2x80x9cbendxe2x80x9d is necessary to advance further to the desired position in the vessel or to advance into another vessel. The distal tip of the guide wire may also acquire an inappropriate bend during advancement of the guide wire in the vessel. For example, the distal tip of the guide wire may prolapse when movement of the tip is impeded and the guide wire is advanced further in the vessel.
When it is determined that the configuration of the guide wire is inappropriate for advancement in the vessel, the guide wire is typically exchanged for a guide wire having the desired configuration. With an over-the-wire type catheter, the guide wire can be withdrawn through the lumen of the catheter and a second guide wire can be installed while leaving the catheter in position. However, with a single-operator exchange type catheter, a guide wire exchange cannot readily be performed without withdrawing the catheter. Once the distal end of the first guide wire is withdrawn proximally from the proximal guide wire lumen opening of the catheter, a second guide wire cannot readily be positioned in the proximal guide wire lumen opening without also withdrawing the catheter so that the proximal guide wire lumen opening is outside the body of a patient.
To derive the benefits achieved from use of an over-the-wire catheter and a single operator exchange catheter, while overcoming the deficiencies of each, Scopton et al. disclose a convertible catheter assembly which includes both an over-the-wire capability and a single operator exchange capability. The Scopton et al. disclosure is made in PCT Application No. WO 92/17236, published on Oct. 15, 1992 and entitled xe2x80x9cADJUSTABLY STIFFENABLE CONVERTIBLE CATHETER ASSEMBLYxe2x80x9d. The disclosure of Scopton et al. is incorporated herein by reference. The Scopton et al. design includes three separate lumens in the proximal portion of the catheter shaft including an inflation lumen, a guide wire lumen and a stiffening mandrel lumen. A side hole is provided through the wall of the catheter shaft at a location close to a distal portion of the catheter. The side hole extends into the guide wire lumen, and has a valve-like cover flap. As is typical for most rapid-exchange type catheters, the column strength of the catheter shaft at the location of the side hole is significantly reduced. Thus, a problem with many rapid exchange type catheters is that the catheter may kink or otherwise fail at the location of the side hole.
When the system design is used in the over-the-wire configuration, a guide wire extends through the full length of the guide wire lumen as described above, and provides additional column support for the entire catheter shaft. A stiffening mandrel is also provided in the stiffening mandrel lumen to provide additional column support. The stiffening mandrel extends out of the proximal end of the catheter shaft, and can be selectively inserted or withdrawn within the stiffening mandrel lumen to control or vary the stiffness of the catheter shaft.
When the Scopton design is used in the rapid-exchange configuration, the guide wire occupies a position adjacent and exterior to the shaft along proximal and intermediate portions of the catheter, and enters a short guide wire lumen of the catheter via the side hole. Thus, in this configuration, the guide wire does not provide additional column support to a majority of the catheter shaft, including at and just proximal to the side hole. This is particularly problematic since the distal portion of the catheter is typically formed from a more flexible material than the proximal portion to facilitate the trackability of the catheter over the guide wire. To compensate for this, Scopton et al. suggest providing the distal most end of the stiffening mandrel distal of the location of the side hole. Thus, the stiffening mandrel may provide some support to the distal end of the catheter, and particular the portion adjacent the side hole. Scopton et al. also suggest that a second stiffening mandrel may be placed in the guide wire lumen proximal of the side hole, providing additional column support to the portion of the catheter shaft that is proximal of the side hole.
A limitation of the Scopton et al. design is that the force provided to the stiffening mandrel during navigation of the catheter through the vascular must be transmitted back to the proximal end of the catheter shaft, which may be a substantial distance. Further, the lumen that receives the stiffening mandrel has a diameter that allows the stiffening mandrel to laterally move therein. Under some circumstances, the stiffening mandrel may bend or otherwise become deformed within the lumen, thereby reducing the effectiveness of the force transmission provided thereby. Another limitation is that the stiffening mandrel does not directly support the weakest portion of the catheter shaft, namely, the portion adjacent the side port. The regions of the catheter that the stiffening mandrel engages during a particular procedure is arbitrary and unpredictable, and highly dependent on the shape of the tortuous path traversed by the catheter. There is therefore a need in the art for a catheter design that increases the force transmission from a stiffening mandrel or core wire to a stiffer more proximal portion of the catheter. There is also a need in the art for a catheter design that directly provides column support at or near the side port of a convertible or rapid exchange type of catheter.
Briefly stated, the present invention is directed to a method and apparatus for increasing the force transmission from a core wire to a more proximal portion of the catheter, and for directly providing column support at or near the side port of a convertible or rapid-exchange type of catheter. A core wire is typically attached to a proximal portion of a catheter, and extends distally therefrom through a lumen in the catheter. In accordance with the present invention, the core wire has a size and shape relative to the lumen of the catheter such that the lateral movement of the core wire is restricted in a restriction region. It has been found that by restricting lateral movement of the core wire at a distal location relative to the proximal catheter portion, the force transmission from the core wire to the proximal catheter portion can be increased. Further, in a rapid exchange or convertible type configuration, the restriction region may be placed; proximate the side hole. By restricting the movement of the core wire adjacent to the side hole, the core wire can provide direct column support thereto reducing the likelihood of kinking or the like at that location.
It is contemplated that the restriction region may extend the entire length of the core wire or any portion thereof. When the restriction region extends over the entire core wire, the core wire may provide additional column support to a substantial portion of the catheter shaft. Likewise, the force transmission from the distal end of the core wire to the proximal end would be substantially increased.
In one illustrative embodiment of the present invention, a shaft having a proximal portion and distal portion is provided. The distal portion is made flexible to increase the trackability of the catheter over the guide wire. The proximal portion of the shaft is made less flexible than the distal portion to increase the column strength, and thus the pushability of the catheter. A lumen extends longitudinally through the shaft of the catheter and has a restriction region distally of the proximal portion of the shaft. A core wire, operably attached to the proximal portion of the shaft, extends distally through the lumen and into the restriction region. The core wire has a size and shape relative to the restriction region of the lumen such that the lateral movement of the core wire is restricted more in the restriction region than outside of the restriction region.
To restrict the movement of the core wire in the restriction region, it is contemplated that the core wire may have an increased dimension in the restriction region, or the lumen of the shaft may have a reduced dimension, or a combination thereof. To decrease the dimension of the lumen of the shaft, an insert tube may be provided at a location that corresponds to the restriction region. To increase the dimension of the core wire, a restriction tube, bump or a bend may be provided at a location that corresponds to the restriction region. Likewise, the core wire may have a flattened portion, wherein the flattened portion has an increased outer dimension relative to a non-flattened portion. The flattened portion of the core wire may further be twisted, preferably between 90 and 360 degrees.
In another illustrative embodiment, a catheter is provided that has an outer tube, a distal inner tube and a proximal inner tube. The proximal inner tube is stiffer than the distal inner tube. The distal end of the proximal inner tube is attached to the proximal end of the distal inner tube, thereby forming an inner tube assembly. The inner tube assembly is disposed within the lumen of the outer tube, and has an outer surface that is spaced from at least a portion of the inner surface of the outer tube, defining a core wire receiving lumen therebetween. The core wire receiving lumen has a restriction region and a non-restriction region, as described above. The core wire is disposed in the core wire receiving lumen, and attached to the stiffer proximal inner tube. The core wire has a size and shape relative to the core wire receiving lumen such that lateral movement of the core wire is restricted more in the restriction region than in the non-restriction region The catheter may include a balloon secured proximate the distal end of the catheter. In this configuration, the core wire receiving lumen may also function as an inflation lumen. As indicated above, the tolerance between the core wire and the inner surface of the core wire receiving lumen is preferably greater in the non-restriction region than in the restriction region. Because the core wire receiving lumen may function as an inflation lumen, the core wire may have an outer surface that is shaped relative to the core wire receiving lumen such that lateral movement of the core wire is restricted more in the restriction region that in the non-restriction region, and also allows substantial fluid flow past the restriction region.
The inner tube assembly preferably has a guide wire lumen extending therethrough. In an over-the-wire configuration, the guide wire is provided through the guide wire lumen, and out the distal end thereof. To provide a rapid-exchange configuration, a side port is provided through the outer tube and inner tube assembly to provide access to the guide wire lumen. Preferably, the restriction region is proximate the side port so that the core wire can provide direct column support thereto.
In yet another illustrative embodiment, a catheter is provided that has an outer tube, a proximal inner tube and an inflation tube. The proximal inner tube is disposed within a proximal portion of the lumen of the outer tube. The inflation tube is also disposed in the lumen of the outer tube, adjacent the proximal inner tube, but extends nearly the full length of the outer tube. A guide wire lumen extends through the proximal inner tube and distally between the inner surface of the outer tube and the outer surface of the inflation tube. A core wire is preferably attached to the proximal inner tube extending distally in the guide wire lumen.
To provide a core wire restriction mechanism, a guide wire receiving tube may be provided in the guide wire lumen distal of the proximal inner tube. The guide wire receiving tube is preferably attached to the inner surface of the outer tube, and laterally spaced from at least a portion of the inflation tube. Thus, a restriction lumen is formed between the restriction tube and the inflation tube. A distal portion of the core wire extends through the restriction lumen. The core wire has a size and shape relative to the restriction lumen such that lateral movement of the core wire is restricted more in the restriction lumen than outside of the restriction lumen.
In an over-the-wire configuration, the guide wire may be provided through the guide wire lumen, through the guide wire receiving tube, and out the distal end of the catheter. In a rapid-exchange configuration, a side port is provided through the outer tube and the guide wire receiving tube to provide access to the guide wire lumen. The guide wire may then extend through the side port, into the guide wire receiving lumen, and out the distal end of the catheter. Preferably, the restriction region is proximate the side port so that the core wire can provide direct column support thereto.
The present invention, together with further objects and advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.